Fatigue, weight change, dry skin and feeling unusually cold are often associated with an underactive thyroid, but these symptoms are not specific enough to diagnose thyroid disease. NICE guidance recommends thyroid testing when there is clinical suspicion, while also warning that one symptom alone may not indicate a thyroid disorder. Diagnosis should therefore combine symptoms, medical history and appropriate blood testing.
What does the thyroid gland do?
The thyroid is a small gland in the neck.
Its hormones influence many processes, including:
- Metabolism
- Heart rate
- Body temperature
- Bowel function
- Energy levels
- Menstrual cycles
- Growth and development
When thyroid hormone levels are too low, the condition is called hypothyroidism.
When they are too high, the condition is called hyperthyroidism.
What symptoms may occur with an underactive thyroid?
Possible symptoms include:
- Fatigue
- Feeling cold
- Constipation
- Dry skin
- Weight gain
- Slower thinking or concentration difficulties
- Muscle aches
- Menstrual changes
- Low mood
- Hair changes
These symptoms overlap with many other conditions.
For example, anaemia, sleep problems, depression, diabetes, nutritional deficiencies or medication effects can also cause fatigue.
A symptom checklist is therefore not a diagnosis.
What about an overactive thyroid?
Hyperthyroidism may produce a different pattern.
Possible features include:
- Palpitations
- Heat intolerance
- Tremor
- Unexplained weight loss
- Sweating
- Anxiety
- Frequent bowel movements
- Menstrual changes
- Muscle weakness
Again, another medical condition may cause similar symptoms.
What tests are normally used?
For adults in whom a pituitary cause is not suspected, NICE recommends considering TSH as the initial thyroid-function test. If TSH is outside the reference range, additional thyroid hormone measurements may be performed according to the result.
Testing strategy may differ in children, pregnancy or suspected pituitary disease.
The result should be interpreted against the laboratory’s reference range and the person’s individual circumstances.
Can supplements interfere with thyroid tests?
Yes.
NICE specifically recommends asking about biotin intake because high intake from supplements may cause misleading thyroid laboratory results.
Patients should therefore tell the clinician about vitamins, hair-and-nail supplements and other over-the-counter products.
They should not stop essential prescribed medicine unless instructed.
What is subclinical hypothyroidism?
This term is used when TSH is raised but thyroid hormone measurements remain within the relevant reference range.
It does not mean every patient automatically needs medication.
Management depends on factors such as TSH level, symptoms, age, repeat measurements and other evidence of thyroid disease.
NICE recommends different approaches according to these factors rather than automatically treating every mildly abnormal test.
How is confirmed hypothyroidism treated?
NICE recommends levothyroxine as first-line treatment for primary hypothyroidism.
The dose requires monitoring.
Taking more thyroid hormone than prescribed in an attempt to increase energy or lose weight can cause harm, including heart-rhythm problems and other complications.
Thyroid medicine should not be marketed as a general weight-loss treatment.
When should thyroid testing be discussed?
A clinician may consider testing when symptoms and history raise reasonable suspicion.
Testing is also relevant in certain medical contexts, including some autoimmune conditions and new-onset atrial fibrillation, as described in NICE guidance.
A new neck swelling, hoarseness, difficulty swallowing or rapidly enlarging thyroid lump should be assessed rather than managed only with routine blood testing.
Where does general medicine fit?
A general physician can assess symptoms in the wider context rather than assuming the thyroid is responsible.
Cura Hospitals’ general medicine service currently includes thyroid and endocrine disorders alongside diabetes, hypertension, infections and other medical conditions. Readers with unexplained symptoms can review its information about thyroid and endocrine disorder evaluation.
Seek prompt medical care for severe palpitations, chest pain, fainting, serious breathing difficulty, confusion or another rapidly worsening symptom.
This article is intended for general education and does not replace thyroid testing, diagnosis or personalised medical treatment.
